In the field of internal combustion engines there are a plurality of access ports which communicate with various portions of the engine, for example, an oil filler hole or a crankcase vent wherein fumes from the crankcase are fed via a tubular member to the combustion system of the engine. A common device for closing such access ports is generally a rotatable cap consisting of several pieces, generally metallic, which often require special preparation of the aperture with which they are associated. Such devices will generally include a single spring-loaded gasket or similar means for purposes of sealing the closing member relative to the access port and providing a barrier to the passage of oil and fumes. Due to the metallic nature of this prior art, the closure means or caps become quite hot from the operating temperature of the engine and hence require insulating means to protect the hand of the mechanic servicing the engine. Failure of such devices often occurs due to the spring fatigue in the locking means as well as failure of the gasket due to wear and repeated compression. In addition, the complex operations required to form the collars and facing elements on the apertures used with prior art caps increases the manufacturing cost of the engine.
As the prior art caps employ a single gasket or sealing member, a failure thereof or momentary overpressure may cause the communication of fumes or fluids through the barrier.
Due to the increased reliance upon such caps to maintain positive crankcase pressure and to meet other requirements placed upon the modern automobile engine, failure of the sealing function presents a substantial impediment to the proper operation of the engine.